Walter Baade

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Baade, Walter

(väl`tər bä`də), 1893–1960, German-born American astronomer. From 1919 to 1931 he was on the staff of the Hamburg observatory; from 1931 to 1958, at the Mt. Wilson observatory. Baade studied the Andromeda Galaxy, M31, and other spiral galaxies and presented evidence for the existence of two different stellar populationsstellar populations,
two broadly contrasting distributions of star types that are characteristic of different parts of a galaxy. Population I stars are young, recently formed stars, whereas population II stars are old and highly evolved.
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, the younger Population I, and the older Population II. From these data he inferred that similar spiral patterns could be found in the Milky Way. Perhaps his most important contribution came in 1952 from observations of Cepheid variablesCepheid variables
, class of variable stars that brighten and dim in an extremely regular fashion. The periods of the fluctuations (the time to complete one cycle from bright to dim and back to bright) last several days, although they range from 1 to 50 days.
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 in nearby galaxies through the 200-in. reflecting telescope at the Palomar Observatory; he calculated that it was necessary to double the cosmic-distance scale, i.e., the distances between external galaxies and the Milky WayMilky Way,
the galaxy of which the sun and solar system are a part, seen as a broad band of light arching across the night sky from horizon to horizon; if not blocked by the horizon, it would be seen as a circle around the entire sky.
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. With Fritz Zwicky and Rudolf Minkowski he distinguished two types of supernovasupernova,
a massive star in the latter stages of stellar evolution that suddenly contracts and then explodes, increasing its energy output as much as a billionfold. Supernovas are the principal distributors of heavy elements throughout the universe; all elements heavier than
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 based on their spectra and on their maximum absolute magnitudes. In 1949 he discovered Icarus, an asteroid whose orbit takes it close to Earth.


See W. Baade, Evolution of Stars and Galaxies (1963).

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References in periodicals archive ?
Walter Baade, the German astronomer who defined the category of bright stellar explosions as "supernovae" in 1934, reexamined Tycho's data to produce a light curve smoothed by quarter-magnitude steps.
His thesis under Walter Baade was on a massive study of novae in M31 which was highly significant for the use of novae as distance indicators.
What they do know (which was first hypothesized by Caltech astronomer Fritz Zwicky and his colleague Walter Baade in 1934) is that when such a star runs out of fuel, it can no longer support itself against gravity's pull, and the star begins to collapse in upon itself, forming what is called a proto-neutron star.
Zwicky's lofty ideas were often wild and woolly, ultimately pulling him away from quantum mechanical studies and into astrophysics, where he and his Caltech cohort and sometime foil, the German emigre Walter Baade, studied superluminous stellar explosions.
This didn't mean astronomers clung to the notion that we were "special." The distances to all other galaxies, hence their deduced physical sizes, would double in the 7950s following Walter Baade's landmark reevaluation of how Cepheid variable stars are used as distance indicators.
I remember roaming the observatory grounds and thinking about all the great astronomers--Edwin Hubble, Walter Baade, Harlow Shapley, and others--who revolutionized 20th-century science using its 60- and 100-inch reflectors.
When their light is combined, the 24.5-meter (80-foot) GMT will have 11 times the light-gathering power of one of its Magellan predecessors, the G.5-meter Walter Baade and Landon Clay telescopes at Chile's Las Campanas Observatory.
One of these was by Walter Baade in 1953, using the apparent brightnesses of 36 RR-Lyrae-type [pulsating] variable stars nearly in the direction of the galactic nucleus.
German emigre Walter Baade (pictured below), who was declared an enemy alien and restricted to the Los Angeles area, used the temporarily dark skies at the Mount Wilson Observatory to make a major discovery.
He has known firsthand many of the great astronomers on the MWO roster, including Hubble, Walter Baade, Rudolph Minkowski, and Alfred Joy.
Recognition of the true character of supernovae did not occur until 1933, when Walter Baade and Fritz Zwicky, at Mount Wilson, explained how energetic and exotic these star-killing explosions must be.